Method and system for signaling transmission layers for single user and multi user MIMO

ABSTRACT

A method and system to signal transmission layers or dedicated reference signal ports to be used in a multiple input multiple output system, the method including providing a downlink control signal containing information for transmission layers or dedicated reference signal ports utilized, the dedicated reference signal ports being associated with the transmission layers; and using the information to demodulate data on each transmission layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.15/882,570, filed on Jan. 29, 2018, now U.S. Pat. No. 10,425,934, whichis a continuation of U.S. application Ser. No. 14/946,371, filed on Nov.19, 2015, now U.S. Pat. No. 9,883,501, which is a continuation of U.S.application Ser. No. 13/328,772, filed on Dec. 16, 2011, now U.S. Pat.No. 9,219,583, which is a bypass continuation application which claimsthe benefit under 35 U.S.C. § 120 of PCT Patent Application No.PCT/US2010/038487, filed Jun. 14, 2010, entitled “Method and System forSignaling Transmission Layers for Single User and Multi User MIMO,”which claims priority to U.S. Provisional Application No. 61/218,705,filed Jun. 19, 2009. These applications include exemplary systems andmethods and are incorporated by reference in their entireties.

FIELD OF THE DISCLOSURE

The present disclosure relates to Multiple Input, Multiple Output (MIMO)communication and in particular to dedicated reference signal usage fordemodulation data in MIMO systems.

BACKGROUND

In Long Term Evolution (LTE) Release 8 (Rel-8) specifications, MultiUser Multiple Input, Multiple Output (MU-MIMO) transmission is supportedin downlink transmission by using transmission mode 5 in the physicallayer. If MU-MIMO is specified in such transmission mode, a UserEquipment (UE) will feedback a Precoding Matrix Indicator (PMI) andChannel Quality Indicator (CQI) to an Evolved Universal TerrestrialRadio Access Network (E-UTRAN) Node B (eNB) and the eNB will scheduletwo or more UEs together and signal to the UEs the precoding matricesused for transmission. The transmit power to each UE may then beproperly scaled to maintain a constant total transmit power and suchpower scaling factor may also be signaled to the UE.

The UE will use a Common Reference Signal (CRS) for channel estimation.Thus, other than the power scaling, the MU-MIMO scheme under Rel-8 isalmost the same as a closed loop Single User MIMO (SU-MIMO) schemewithout any special treatment for MU-MIMO.

In LTE Advanced (LTE-A), various features are being considered. Amongthem are that the reference signal (RS) is defined into two categories,one for Channel Measurement (CSI-RS) and the other for Demodulation(DM-RS). This is different from the Rel-8 specifications, where channelestimation and demodulation all use the same set of common referencesignals, the CRS. Furthermore, the DM-RS should be pre-coded in the sameway as for data, making the RS a Dedicated Reference Signal (DRS).

In LTE Rel-9, a work item being investigated is the performance of adual layer beamforming technique. In such a system, two independent datastreams are encoded, modulated and mapped to frequency resources. Thedata streams are then transmitted on two independent beams from a set ofantennas, a subset of which may have low mutual correlation. For examplethe set of antennas could be an array of half wavelength spaced dualpolarized elements or the set could be two panels separated by 4 or morewavelengths, where each panel contains half wavelength spaced elements.DRS is also used for demodulation.

This use of a Dedicated Reference Signal creates problems with regard tocontrol signaling. Efficiency is one design consideration for controlchannels, since control channel overhead impacts system capacity.

Efficient control signaling schemes have been developed in the area ofresource allocation. In particular, in order to allocate one or more ofa plurality of radio resources, several signaling schemes have beendeveloped. For example, if there are N radio resources, then a bitmap oflength N, where each bit represents one radio resource, can be used toindicate a resource allocation. Alternatively, if there are N radioresources, then a first signaling field can be used to indicate thefirst radio resource in a resource allocation and a second signalingfield can be used to indicate the number of radio resources in theallocation. Efficient signaling is also desirable for DRS.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will be better understood with reference to thedrawings in which:

FIG. 1 is a block diagram showing configuration of multi user multipleinput multiple output communications in a long term evolution release 8system;

FIG. 2 is a block diagram showing beamforming communication between abase station and a single user;

FIG. 3 is a block diagram showing beamforming communication between abase station and multiple users in which the same beams are provided toeach user;

FIG. 4 is a block diagram showing beamforming communication between abase station and multiple users in which separate beams are provided toeach user;

FIG. 5 is a block diagram showing multi user multiple input multipleoutput communications in which separate layers are provided to differentuser equipment;

FIG. 6 is a block diagram showing a multi cell implementation of thesystem of FIG. 5;

FIG. 7 is a block diagram showing a dedicated reference signal pattern;

FIG. 8 is a block diagram showing layer assignment grouped for eachreceiver;

FIG. 9 is a block diagram showing layer assignment grouped for eachreceiver in which the assignment wraps from a last layer to a firstlayer;

FIG. 10 is a block diagram showing communications between a networkelement and a user equipment in which dedicated reference signalpatterns/codes or ports are derived; and

FIG. 11 is a block diagram of an exemplary user equipment.

DETAILED DESCRIPTION

The present disclosure provides a method to signal transmission layersto be used in a multiple input multiple output system comprising:providing a downlink control signal containing information fortransmission layers or dedicated reference signal ports utilized, thededicated reference signal ports being associated with the transmissionlayers; and using the information to demodulate data on eachtransmission layer.

The present disclosure further provides a network element configured tosignal transmission layers and/or DRS patterns/codes or DRS ports to beused in a multiple input multiple output system comprising: acommunications subsystem for providing a downlink control signalcontaining information for transmission layers and/or DRS patterns/codesor DRS ports utilized.

The present disclosure still further provides a method at a userequipment for utilizing information for transmission layers to be usedin a multiple input multiple output system comprising: receiving adownlink control signal containing information for transmission layersor dedicated reference signal ports utilized, the dedicated referencesignal ports being associated with the transmission layers; anddemodulating a signal based on the information.

The present disclosure still further provides a user equipmentconfigured to use signaling for transmission layers and/or DRSpatterns/codes or DRS ports in a multiple input multiple output systemcomprising: a communications subsystem for receiving a downlink controlsignal containing information for transmission layers and/or DRSpatterns/codes or DRS ports utilized; and a processor for demodulating asignal based on the information for transmission layers and/or DRSpatterns/codes or DRS ports utilized.

Reference is now made to FIG. 1. As shown in FIG. 1, a Rel-8 Multi-UserMIMO transmission is shown. If specified that the UE is in transmissionmode 5, the UE provides a precoding matrix indicator (PMI) and channelquality indicator (CQI) to the eNB and the eNB then schedules two ormore UEs together and signals to the UEs the precoding matrices used fortransmission.

Thus, as seen in FIG. 1, a UE 110 and a UE 120 both provide signals toeNB 130, through a base station 140, with the CQI and PMI, as shown byarrows 142 and 144 respectively.

In response, the eNB 130, through base station 140, pairs the UEs 110and 120 and starts the MU-MIMO transmission, as shown by arrows 152 and154.

Conversely, in LTE-A various options exist. Among them are dividing thereference signal into two categories, one for channel measurement andone for demodulation. The reference signals for demodulation areprecoded in the same way as the data and thus become dedicated resourcesignals. One reason for introducing DRS as DM-RS is to control theresource signaling overhead in high order MIMO (where a large number ofchannels or layers are enabled). In LTE-A, high order MIMO would requiremore overhead if the common reference signal is used.

The introduction of the DRS for LTE-A may facilitate the use ofMulti-User MIMO. Namely, the use of DRS requires no explicit signalingof the power level to the UE since the power level information iscarried by the DRS. Also, due to the use of DRS, the eNB could usedifferent precoding matrices other than the one recommended by the UE,and it could even use a precoding matrix not specified in a codebook.The use of such precoding matrices may facilitate interferencesuppression and cancellation in MU-MIMO. Furthermore, the PMI need notbe signaled by the eNB to the UE to save control signal overhead in oneembodiment. The use of DRS also allows more flexibility for the MU-MIMOtransmission such as layer allocation.

In LTE Rel-9, beamforming techniques and design aspects are considered.In such a system, two independent data streams are encoded, modulatedand mapped to frequency resources. The data streams are then transmittedon two independent beams from a set of antenna with cross polarization.DRS is used for demodulation.

Reference is now made to FIG. 2. As seen in FIG. 2, a UE 210communicates with an eNB 220 through a base station 230. In theembodiment of FIG. 2, a single user MIMO has dual layer beamforming, asshown by beams 240 and 242 respectively.

Referring to FIG. 3, a UE 310 and UE 320 communicate with an eNB 330through base station 340. Each UE 310 and 320 receive 2 beams, shown asbeams 350 and 352.

Reference is now made to FIG. 4. In FIG. 4, UEs 410 and 420 communicatewith an eNB 430 through a base station 440. In the example of FIG. 4, adual layer beam forming for Multi-User MIMO is provided with differentbeams. The different beams are shown as beam 450, provided to UE 410,and beam 452, provided to UE 420.

As seen from FIGS. 2, 3 and 4, two independent data streams aremodulated and mapped to frequency resources. They are then transmittedon two independent beams from a set of antennas, a subset of which mayhave low mutual correlation. For example the set of antennas could be anarray of half wavelength spaced dual polarized elements or the set couldbe two panels separated by 4 or more wavelengths, where each panelcontains half wavelength spaced elements. DRS is used for demodulation.

FIGS. 2 to 4 show that the system of Rel-9 has the flexibility tosupport Single User MIMO as well as Multi-User MIMO transmission and canhave the flexibility of transmitting to two users, each on a differentbeam or layer.

The transmission flexibility in Rel-9 and LTE-A requires a correspondingnew control signal design to avoid the introduction of too many modesand too many transmission configurations, as the introduction of toomany modes and configurations will increase the complexity of both theeNB and UE.

Furthermore, even though Multi-User MIMO may provide performancebenefits for Rel-9 and LTE-A, some issues may need to be addressed,other than by using the dedicated reference signals. This is because,unlike using the Single-User MIMO, there is flexibility in Multi-UserMIMO configurations and transmissions to be considered in the design ofcontrol signaling.

Reference is now made to FIGS. 5 and 6. FIGS. 5 and 6 show two examplesof Multi-User MIMO transmission in both single cell and multi-celltransmission (CoMP).

Specifically, in FIG. 5, a single cell, multi user MIMO system isprovided where various layers are transmitted to different UEs. Inparticular, in FIG. 5, UE 510 receives a layer 512 from the eNB 520through a base station 522.

UE 530 receives layers 532 and 534 from the eNB 520.

Referring to FIG. 6 a multi-cell approach is shown in which a UE 610receives a layer 612 from both eNB 620 and eNB 630 through base stations622 and 632 respectively.

UE 640 receives beams 642 and 644 from eNB 620 and eNB 630 in theexample of FIG. 6.

As will be appreciated, FIGS. 5 and 6 show downlink transmissions, whichcould mean different layers being transmitted or it could mean actualbeams. From the figures, three beams are provided, two being provided toone UE, while the third is

However, mixed layer transmission is not supported by current Rel-8control signaling. This is because the current Rel-8 control signal onlycontains information of transmit rank (TR), which is enough to supportSingle User MIMO or Multi-User MIMO whereas CRS is used as the DM-RS.However, for Rel-9 and LTE-A, as DRS is used for MU-MIMO as DM-RS, andDRSs on different layers are orthogonal to each other, rank informationis not sufficient for the UE to perform demodulation.

Specifically, reference is made to FIG. 7. As shown in FIG. 7, a DRSpattern 710 has two sets of DRS for each layer, namely DRS for layer 1720 and DRS for layer 2 722. The DRS for layer 1 720 and DRS for layer 2722 are orthogonal to each other. If the eNB configures the MU-MIMOtransmission on 2 UEs, each with a different layer, then simplysignaling to the UE the rank-1 transmission is not enough as the UE mustalso know on which layer it is going to receive the transmission and touse the appropriate DRS for demodulation.

Furthermore, in Rel-8 standards, SU-MIMO and MU-MIMO are two separatetransmission modes. However, in LTE-A it may be desirable to have suchmodes merged into one MIMO mode to support dynamic switching betweenSU-MIMO and MU-MIMO without awareness of the UE.

Various control signaling options are provided below.

1. Bitmap Approach

In a first embodiment, one way to signal the transmitted layers indownlink control signals is to use a bitmap. Thus, for example, for2-layer transmission, a 2-bit bitmap could be included in the DownlinkControl Information (DCI). A first bit “1” means the corresponding layeris scheduled for transmission, while a bit value of “0” means that thelayer is not scheduled for transmission.

Thus, the following bit combinations for a 2-bit bitmap could have thefollowing meanings assuming layer index starting from 0

[1 0]—This means that layer 0 is scheduled for transmission

[0 1]—This means that layer 1 is scheduled for transmission

[1 1]—This means that both layers are scheduled for transmission

Since both in Long Term Evolution (LTE) Rel-9 specifications, and alsoin LTE-Advanced (LTE-A), each layer has its corresponding dedicatedreference signal (DRS) to demodulate the corresponding layer. For SingleUser MIMO, all the above 3 bit combinations could be used to indicatesingle-layer transmission or full-rank transmission.

For Multi User MIMO transmission where two users could be scheduled atthe same time, if each UE is scheduled to receive on a different layer,then bitmap [1 0] could be signaled to the first UE and bitmap [0 1]could be signaled to the second UE.

As will be appreciated by those skilled in the art, the above bitmap notonly contains layer information, it also contains Transmitted Rank (TR)information. Specifically, the bitmap [1 0] simply means a rank-1transmission is scheduled, while a bitmap of [1 1] means a full ranktransmission is scheduled.

In this regard, bitmap signaling not only solves an issue that layerinformation is missing from the downlink control signal in LTE Rel-8,but also makes SU-MIMO and MU-MIMO transparent to the UE, as the sameDCI format could be used for SU-MIMO and MU-MIMO and a UE does not haveto be aware if it is in SU-MIMO mode or MU-MIMO mode.

Referring to Table 1 below, Table 1 provides a bitmap method for a2-layer transmission and summarizes the above.

TABLE 1 Bitmap method for 2-layer transmission Layer index Transmitted(2 bits) Interpretation Rank (TR) [1 0] Layer (beam) 0 is 1 transmitted[0 1] Layer (beam) 1 is 1 transmitted [1 1] Both layer (beam) are 2transmitted

As seen in Table 1 above, the bitmap corresponds with the layer that istransmitted and also provides the transmitted rank.

For dual-layer Beamforming (BF) schemes for Rel-9, such signaling couldbe used as well to provide enough flexibility for supporting SU-MIMO andMU-MIMO.

The above 2-bit bitmap is scalable and could be extended for 4-layertransmission or 8-layer transmission.

For 4-layer transmission (also called rank-4 transmission herein) LTE-A,a 4-bit bitmap could be used and some examples of such a bitmap follow.

Specifically:

-   -   [1 1 0 0]—Could mean that layers 0 and 1 are scheduled for        transmission, with a transmitted rank of 2.    -   [0 1 0 0]—Means that layer 1 is scheduled for transmission and a        transmitted rank of 1.    -   [1 1 1 1]—Means that all 4 layers are scheduled for transmission        and a transmission rank of 4 is assigned.

Utilizing the same convention, for 8-layer transmission in LTE-A, an8-bit bitmap could be used.

The bitmap method, in summary, is used with the number of bitsequivalent to the maximum number of layers that could possibly betransmitted. The total number of layers possibly being transmitted wouldbe the same as the total number of virtual transmit antennas in singlecell transmission, or total number of combined transmit antennas fromdifferent transmit points in Coordinated Multiple Point (CoMP)transmission. Any bit in the bitmap could use values of either 1 or 0,with a value “1” meaning that the corresponding layer will betransmitted to the UE and with the value “0” meaning that thecorresponding layer will not be transmitted to the UE. Such bitmap istransmitted and may be associated with the DCI and could vary fromsubframe to subframe, reflecting the fact that different numbers oflayers could be transmitted from subframe to subframe.

In an alternative embodiment, similar to the bitmap approach above, isto utilize the index of layer allocation information. Specifically, inthe case of 4 layers there are a total of 15 different combinations. Bysorting these 15 combinations in order, the eNB may signal an indexvalue to the UE of 4 bits. In the case of 8 layers, there are a total of2 exp 8−1=255 different combinations. By sorting them in order, the eNBsignals an index value of 8 bits to the UE.

The alternative embodiment is described below with regard to Table 2which shows an example of an index value that is passed from the eNB tothe UE. The index corresponds with the bitmap shown in Table 2 below,for example.

TABLE 2 Indices for 4-layer transmission Index Value Layer Bitmap 0 [0 00 1] 1 [0 0 1 0] 2 [0 1 0 0] 3 [1 0 0 0] 4 [0 0 1 1] 5 [0 1 0 1] 6 [1 00 1] 7 [0 1 1 0] 8 [1 0 1 0] 9 [1 1 0 0] 10 [0 1 1 1] 11 [1 0 1 1] 12 [11 0 1] 13 [1 1 1 0] 14 [1 1 1 1]

In yet a further possible embodiment, a field may be composed of twoparts. The first part is a subset indicator, while the second field isthe index of the element in the subset. For example, if we divide allcombinations into 2 sets, one for SU-MIMO and the other for MU-MIMO,then the first subset indicator is 1-bit. That is, if the first subsetindicator is a “0”, it is for SU-MIMO subsets. Otherwise it is MU-MIMOsubsets. Such subset indicator could be implicitly signaled by otherparameters which indicates the SU-MIMO and MU-MIMO transmission.Assuming there are a total of 4 layers, the second field for the SU-MIMOsubset is a 2 bit element index. The second field for the MU-MIMO subsetcould be a 3-bit element index. Thus, an extra padding bit could beadded to the SU-MIMO element index to align its DCI format with that ofthe MU-MIMO if a unified DCI format is desired.

In particular, the use of an indicator bit with a subset is illustratedbelow.

TABLE 3 Subset indicator for 4-layer transmission Subset Element LayerIndicator Index Bitmap Definition [0] 0 [1 0 0 0] SU-MIMO - Layer 0 [0]1 [1 1 0 0] SU- MIMO - Layer 0 and 1 [0] 2 [1 1 1 0] SU MIMO- Layer 0, 1and 2 [0] 3 [1 1 1 1] SU MIMO - Layer 0, 1, 2 and 3 [1] 0 [1 0 0 0] MU -MIMO - layer 0 [1] 1 [0 1 0 0] MU - MIMO - layer 1 [1] 2 [0 0 1 0] MU -MIMO - layer 2 [1] 3 [0 0 0 1] MU - MIMO - layer 3 [1] 4 [1 1 0 0] MU -MIMO - layers 0 and 1 [1] 5 [0 0 1 1] MU - MIMO - layers 2 and 3 [1] 6[1 1 1 0] MU - MIMO - layers 0, 1and 2 [1] 7 [1 1 1 1] MU - MIMO -layers 0, 1, 2, 3

2. Grouping Assignment Approach

The above bitmap approach covers all arbitrary selection, combinations,which may in some instances not be necessary. A simplified alternativeto the bitmap approach is to assign the layers to each UE together. Forexample, if 3 UEs will be assigned with n1, n2, n3 layers, then thefirst n1 layers could be assigned to the first UE, the next n2 layerscould be assigned to the second UE, and the next n3 layers could beassigned to the third UE.

In particular, reference is now made to FIG. 8. In FIG. 8 a layer indexfor 8 layers is shown. The layer index 800 includes a first layer 810,second layer 812, third layer 814, fourth layer 816, fifth layer 818,sixth layer 820, seventh layer 822 and eighth layer 824.

In the example of FIG. 8, three UEs are transmitting in MU-MIMO. Thefirst UE can be assigned layers 810 and 812, the second UE can beassigned layers 814, 816 and 818, and the third UE can be assignedlayers 820, 822 and 824. The allocation of layers which are adjacent toeach other to a UE corresponds with the grouping assignment approach.

To signal each assignment, a pair of numbers, denoted by (n,m) could bedefined, where n is the index of starting layer for each UE and m is thenumber of layers assigned to the UE. Thus, in the example of FIG. 8,such pair of numbers for each UE could be derived as follows, assumingthat the layer index for layer 810 starts from 0:

UE #1, (0,2)

UE #2, (2,3)

UE #2, (5,3)

Furthermore, the assignment could be used in a more generalizedwrap-around fashion. Reference is now made to FIG. 9. In FIG. 9, two UEsare assigned, one having 3 layers, and the second having 5 layers. Thestarting index and number of layers for each UE could be defined as:

UE #1, (2,3)

UE #2, (5,5)

Referring to FIG. 9, layer 910 has a layer index 900 of 0 and thesubsequent layers, namely layer 912, layer 914, layer 916, layer 918,layer 920, layer 922 and layer 924 could be assigned. In particular, inaccordance with the above, layers 918, 920, 924 are assigned to UE #2.Furthermore, UE #2 has layers 910 and 912 assigned to it since there are5 layers assigned and the process wraps around 2 layers 910 and 912.

Table 4 below summarizes the signaling bits for such an approach for 4layer and 8 layer transmissions. As can be seen in the table, for 4layer transmission there is no overhead reduction for an approach ascompared with a bitmap approach. However, for an 8 layer approach, suchapproach requires 6 signaling bits, which is a 2-bit saving over thebitmap approach.

TABLE 4 Number of signaling bits for grouping assignment approach Totalnumber Bit for index Bit for number Total number of transmis- ofstarting of layers for of signalling sion layers layer “n” each UE “m”bits 4 2 2 4 8 3 3 6

3. Selected Layer Approach

While the bitmap approach described above is simple and straightforward,it may cover arbitrary layer selection combinations. For cases where thetotal number of transmission layers is low, such as 3 or 4 layers, using2-bit or 4-bit bitmaps will not introduce much extra overhead andtherefore might be acceptable. However, for the case where the totalnumber of transmission layers is high, for example 8 layers, using an8-bit bitmap could lead to some concerns regarding control channeloverhead. In order to address the concern of overhead, an alternativegrouping assignment approach is proposed above which may lead to someoverhead reduction for 8 layer transmission.

A further approach is a selected layer approach. The selected layerapproach selectively chooses some combinations of layers for thetransmission. The selection of such layer combination should becarefully made without missing any typical layer combinations. On theother hand, not every arbitrary layer combination layer is meaningfuland therefore leaving out some of the layer combinations should notimpact performance.

Selection of layers may be made based on various criteria. Threecriteria may be used, for example, may include:

1) All transmission layer hypotheses for SU-MIMO should be included;

2) In addition to the layer hypotheses selected for SU-MIMO, extra layerhypotheses for MU-MIMO could also be added; and

3) When the eNB assigns MU-MIMO transmission, it will assign a UE withthe most number of layers first, followed by the UE with the second mostnumber of layers, etc., for example.

Thus, when the eNB assigns two UEs in MU-MIMO, UE #1 having 2 layers andUE #2 having 3 layers, the eNB should assign layers 0 to 2 to UE #2first followed by assigning layer 3 to 4 to UE #1.

The assignment of the most layers first avoids unnecessary combinationsand leads to reduction in the combinations needing to be signaled, thussaving signaling overhead.

An example of layer selection for a 4-layer transmission is illustratedbelow with regard to Table 5.

TABLE 5 Layer selection for total 4-layer transmission Bitmap Per-UEIndications Transmission Index for layers Rank Modes 0 [1 0 0 0] 1SU-MIMO/MU- MIMO 1 [0 1 0 0] 1 MU-MIMO 2 [0 0 1 0] 1 MU-MIMO 3 [0 0 0 1]1 MU-MIMO 4 [1 1 0 0] 2 SU-MIMO/MU- MIMO 5 [0 0 1 1] 2 MU-MIMO 6 [1 1 10] 3 SU-MIMO/MU- MIMO 7 [1 1 1 1] 4 SU-MIMO

Furthermore, for 8-layer transmission, Table 6 provides variouscombinations.

TABLE 6 Layer selection for total 8-layer transmission Bitmap Per-UEIndications Transmission Index for layers Rank Modes 0 [1 0 0 0 0 0 0 0]1 SU-MIMO/MU- MIMO 1 [0 1 0 0 0 0 0 0] 1 MU-MIMO 2 [0 0 1 0 0 0 0 0] 1MU-MIMO 3 [0 0 0 1 0 0 0 0] 1 MU-MIMO 4 [0 0 0 0 1 0 0 0] 1 MU-MIMO 5 [00 0 0 0 1 0 0] 1 MU-MIMO 6 [0 0 0 0 0 0 1 0] 1 MU-MIMO 7 [0 0 0 0 0 0 01] 1 MU-MIMO 8 [1 1 0 0 0 0 0 0] 2 SU-MIMO/MU- MIMO 9 [0 0 1 1 0 0 0 0]2 MU-MIMO 10 [0 0 0 1 1 0 0 0] 2 MU-MIMO 11 [0 0 0 0 1 1 0 0] 2 MU-MIMO12 [0 0 0 0 0 1 1 0] 2 MU-MIMO 13 [0 0 0 0 0 0 1 1] 2 MU-MIMO 14 [1 1 10 0 0 0 0] 3 SU-MIMO/MU- MIMO 15 [0 0 0 1 1 1 0 0] 3 MU-MIMO 16 [0 0 0 01 1 1 0] 3 MU-MIMO 17 [0 0 0 0 0 1 1 1] 3 MU-MIMO 18 [1 1 1 1 0 0 0 0] 4SU-MIMO/MU- MIMO 19 [0 0 0 0 1 1 1 1] 4 MU-MIMO 20 [1 1 1 1 1 0 0 0] 5SU-MIMO/MU- MIMO 21 [1 1 1 1 1 1 0 0] 6 SU-MIMO/MU- MIMO 22 [1 1 1 1 1 11 0] 7 SU-MIMO/MU- MIMO 23 [1 1 1 1 1 1 1 1] 8 SU-MIMO 24-31 Reserved

The above tables show that all possible combinations of layerallocations to multiple UEs can be generated using layer assignmentsshown in the tables. For example, with a total of 8 layers from Table 6,the following layer assignments would be possible:

0-8 UEs with one spatial layer each;

0-4 UEs with two spatial layers each;

0-2 UEs with three spatial layers each;

0-2 UEs with four spatial layers each;

0-1 UEs with five spatial layers each;

0-1 UEs with six spatial layers each;

0-1 UEs with seven spatial layers each; and

0-1 UEs with eight spatial layers each.

Any combination of the above spatial layers assignments is achievableusing a subset of layer assignments given in Table 6 above, providingthat the total number of assigned spatial layers adds up to eight orless.

In one embodiment, Table 5 or 6 above could be modified by flipping thebitmap. For example, the bitmap [1 1 1 1 1 1 0 0] could be flipped tobecome [0 0 1 1 1 1 1 1], which means that the UE with the most layerscould be assigned first starting from the other end of the layerspectrum.

Referring to Tables 5 and 6 above, the bitmap in the second column inthe tables indicates which layers are scheduled and which ones are not.Similar to the tables above with regard to the bitmaps, bit “1” meansthat the corresponding layer is scheduled for transmission, while bit“zero” means that the corresponding layer is not scheduled fortransmission. As will be appreciated, all possible layer selections forSU-MIMO are included and further in addition to those selected forSU-MIMO, some addition layer combinations are selected mainly withMU-MIMO transmission in mind. This allows for the selection of a goodmix for SU-MIMO and MU-MIMO while keeping the number of selectionhypotheses low, but without losing scheduling flexibility.

As would be appreciated by those in the art, Tables 5 and 6 above alsoprovide rank information for information purposes. However, suchinformation may not need to be transmitted to the UE since the UE couldderive such information from bitmap indication for the layers (i.e. thetotal number of bits in the bitmap corresponding to the index).

The left most column provides an index in the table set that transmittedalong with the associated DCI. As seen, from Table 5 above, 3 bits areneeded to signal the rank-4 transmissions and 5 signaling bits areneeded for rank-8 transmissions. This leads to a savings of 1-bit overthe bitmap method above for a rank-4 transmission and a savings of 3bits for a rank-8 transmission as compared with the bitmap method above.

The selected layer combination could be semi-statically configured byRRC signaling which indicates that it could change from time to time, ormay be fixed by the specifications for LTE release 9 or LTE-A.

For example, in an 8-layer case, the selection of layer combinations forMU-MIMO may be different for different UEs. Even for the same UE, theselected layer combination is allowed to be changed during an RRCconnected state.

4. Selecting Layers with Transport Block Enabling Approach

Signaling from above may further be reduced by utilizing informationconcerning the number of transport blocks (TB). In particular, release 8DCI formats 2 and 2A could be modified as a DCI format to carrysignaling to indicate layers assigned to a UE. DCI formats 2 and 2Acarry information for two transport blocks and transport block disablinginformation is included in the DCI. As will be appreciated by those inthe art, if one transport block is enabled while the second one isdisabled, this implies that a maximum rank of 4 is allowed, while if twotransport blocks are enabled then a rank>1 transmission is present (i.e.is two transport blocks are enabled, then no rank equals one isallowed).

For signaling purposes 2 tables could be generated.

Referring to Table 7, when one transfer block is enabled, this table maybe used and contains transmission combinations for ranks up to fourtransmissions.

TABLE 7 Transmission layer combination when one TB is enabled BitmapPer-UE Indications Transmission Index for layers Rank Modes 0 [1 0 0 0 00 0 0] 1 SU-MIMO/MU- MIMO 1 [0 1 0 0 0 0 0 0] 1 MU-MIMO 2 [0 0 1 0 0 0 00] 1 MU-MIMO 3 [0 0 0 1 0 0 0 0] 1 MU-MIMO 4 [0 0 0 0 1 0 0 0] 1 MU-MIMO5 [0 0 0 0 0 1 0 0] 1 MU-MIMO 6 [0 0 0 0 0 0 1 0] 1 MU-MIMO 7 [0 0 0 0 00 0 1] 1 MU-MIMO 8 [1 1 0 0 0 0 0 0] 2 SU-MIMO/MU- MIMO 9 [0 1 1 0 0 0 00] 2 MU-MIMO 10 [0 0 1 1 0 0 0 0] 2 MU-MIMO 11 [0 0 0 1 1 0 0 0] 2MU-MIMO 12 [0 0 0 0 1 1 0 0] 2 MU-MIMO 13 [0 0 0 0 0 1 1 0] 2 MU-MIMO 14[0 0 0 0 0 0 1 1] 2 MU-MIMO 15 [1 0 0 0 0 0 0 1] 2 MU-MIMO 16 [1 1 1 0 00 0 0] 3 SU-MIMO/MU- MIMO 17 [0 1 1 1 0 0 0 0] 3 MU-MIMO 18 [0 0 1 1 1 00 0] 3 MU-MIMO 19 [0 0 0 1 1 1 0 0] 3 MU-MIMO 20 [0 0 0 0 1 1 1 0] 3MU-MIMO 21 [0 0 0 0 0 1 1 1] 3 MU-MIMO 22 [1 0 0 0 0 0 1 1] 3 MU-MIMO 23[1 1 0 0 0 0 0 1] 3 MU-MIMO 24 [1 1 1 1 0 0 0 0] 4 SU-MIMO/MU- MIMO 25[0 1 1 1 1 0 0 0] 4 MU-MIMO 26 [0 0 1 1 1 1 0 0] 4 MU-MIMO 27 [0 0 0 1 11 1 0] 4 MU-MIMO 28 [0 0 0 0 1 1 1 1] 4 MU-MIMO 29 [1 0 0 0 0 1 1 1] 4MU-MIMO 30 [1 1 0 0 0 0 1 1] 4 MU-MIMO 31 [1 1 1 0 0 0 0 1] 4 MU-MIMO

As seen from above, the above is limited to a rank of 4 but providesadditional combinations to those provided above with regard to Table 6.

If both transport blocks are enabled, Table 8 is used, which containstransport layer combinations for rank >1 transmission. As will beappreciated, if both transport blocks are enabled the rank will begreater than one and therefore the rank of “one” can be excluded fromthis table.

TABLE 8 Transmission layer combination when both TB are enabled BitmapPer-UE Indications Transmission Index for layers Rank Modes 0 [1 1 0 0 00 0 0] 2 SU-MIMO/MU- MIMO 1 [0 1 1 0 0 0 0 0] 2 MU-MIMO 2 [0 0 1 1 0 0 00] 2 MU-MIMO 3 [0 0 0 1 1 0 0 0] 2 MU-MIMO 4 [0 0 0 0 1 1 0 0] 2 MU-MIMO5 [0 0 0 0 0 1 1 0] 2 MU-MIMO 6 [0 0 0 0 0 0 1 1] 2 MU-MIMO 7 [1 0 0 0 00 0 1] 2 MU-MIMO 8 [1 1 1 0 0 0 0 0] 3 SU-MIMO/MU- MIMO 9 [0 1 1 1 0 0 00] 3 MU-MIMO 10 [0 0 1 1 1 0 0 0] 3 MU-MIMO 11 [0 0 0 1 1 1 0 0] 3MU-MIMO 12 [0 0 0 0 1 1 1 0] 3 MU-MIMO 13 [0 0 0 0 0 1 1 1] 3 MU-MIMO 14[1 0 0 0 0 0 1 1] 3 MU-MIMO 15 [1 1 0 0 0 0 0 1] 3 MU-MIMO 16 [1 1 1 1 00 0 0] 4 SU-MIMO/MU- MIMO 17 [0 1 1 1 1 0 0 0] 4 MU-MIMO 18 [0 0 1 1 1 10 0] 4 MU-MIMO 19 [0 0 0 1 1 1 1 0] 4 MU-MIMO 20 [0 0 0 0 1 1 1 1] 4MU-MIMO 21 [1 0 0 0 0 1 1 1] 4 MU-MIMO 22 [1 1 0 0 0 0 1 1] 4 MU-MIMO 23[1 1 1 0 0 0 0 1] 4 MU-MIMO 24 [1 1 1 1 1 0 0 0] 5 SU-MIMO/MU- MIMO 25[0 1 1 1 1 1 0 0] 5 MU-MIMO 26 [0 0 1 1 1 1 1 0] 5 MU-MIMO 27 [0 0 0 1 11 1 1] 5 MU-MIMO 28 [1 1 1 1 1 1 0 0] 6 SU-MIMO/MU- MIMO 29 [1 1 1 1 1 11 0] 7 SU-MIMO/MU- MIMO 30 [1 1 1 1 1 1 1 1] 8 SU-MIMO/MU- MIMO 31Reserved

As both Table 7 and Table 8 contain 32 transmission layer combinations,5-bit signaling is enough. This is the same signaling as required forthe method corresponding with Table 6 above. However, when comparingTable 7 and Table 8 with Table 6, there is additional information fortransmission layer combinations which do not exist in Table 6. This isbecause Table 6 follows a criteria that always assigns the UE indescending order of layers. While such assignment may be fine in manysituations, in some scenarios such as Semi-Persistent Scheduling (SPS),reordering layers from sub frame to sub frame to a particular UE may notbe possible. The extra layer combinations provided in Table 7 and Table8 may be beneficial in this case.

The scheme described with reference to Table 7 and Table 8 can begeneralized such that a first mapping of a control channel field to alayer indication is used if there is a first number of transport blocksand a second mapping of a control channel field to a layer indication isused if there is a second number of transport blocks. In someembodiments, the control channel field is represented by the same numberof bits for these two cases.

5. Additional Signaling if DRS Ports are Total Rank Dependent

The above embodiments use a one one-to-one mapping between layers andDRS patterns/codes or DRS ports, where a DRS port is a DRS pattern/codeassociated with a transmission layer and a DRS pattern/code indicatesthe time, frequency, or spreading/scrambling code pattern used totransmit the DRS. However, in some embodiments there could existscenarios where one-to-one layer to DRS mapping may not exist. Forexample, the DRS on layer #1 for total transmission rank of 4 may not bethe same as DRS on layer #1 for total transmission rank of 8. This maybe caused by designs that allow DRS density/patterns on the same layerto be different for different transmission ranks.

In particular, reference is made to FIG. 7 in which various DRSallocations are made for the 2 layers shown in FIG. 7. However, DRS forlayer 1 720 takes 6 resource elements (REs) for each layer. Since thepatterns are orthogonal, the DRS for layer 2, illustrated by referencenumeral 722, must be in different positions. 6 REs are shown for the DRSfor layer 2.

As will be appreciated, if 6 REs per layer are utilized for 8 layers, 48REs in total need to utilized for RS, leaving little room for data.

Thus, in one embodiment, a maximum of 24 REs can be utilized for DRS forthe total rank of all layers. Thus, the DRS may utilize only 3 REs perlayer for an 8 layer embodiment. Conversely, if 4 layers are provided, 6REs per layer are provided.

The capping of total number of DRS could lead to density/patterns of DRSon the same layer which varies based on the transmission ranks. When thetotal transmission layers are low, such as 2 or 4 layers, the DRSpatterns or code could be designed such that they would not change withthe transmission ranks. This would create a one-to-one mapping betweenDRS and layer, where the solutions of Tables 3 to 8 could be used.

For the scenarios where the DRS patterns/codes change with the totaltransmission rank, one solution is to signal the total transmission rankin addition to the layers. This would lead the UE to find thecorresponding DRS for demodulation. Such total transmission rank wouldrequire 3 bits to signal for 8 total transmission layers. Alternativeembodiments could be to signal the total DRS patterns for thetransmission, as the total DRS patterns could be different from thetotal transmission rank. For example, if Code Division Multiplexing(CDM) is used for DRS multiplexing, the total DRS pattern could varywith every second number of ranks. Therefore, rank-3 and rank-4 couldshare the same DRS patterns while rank-7 and rank-8 could share with thesame DRS pattern as well. This makes the total DRS patterns 4, whichonly requires 2 bits to signal.

5.1. Signaling when Transport Block Enabling is Considered

When one transport block is enabled while the other is disabled, 5 bitsare needed for signaling layer combinations. In addition, 2 bits areneeded to signal the total rank of 4, requiring 7 bits in total tosignal both layer combinations and total transmission rank. When two TBare all enabled, 3 bits are required to signal the total rank to 8. Toalign the total number of signaling bits with the scenario where one TBis enabled, the layer combinations for rank>1 contained in Table 6 abovecould be used which, as shown in Table 9 below, requires 4 bits tosignal.

TABLE 9 Rank > 1 transmission layer combination Bitmap Per-UEIndications Transmission Index for layers Rank Modes 0 [1 1 0 0 0 0 0 0]2 SU-MIMO/MU- MIMO 1 [0 0 1 1 0 0 0 0] 2 MU-MIMO 2 [0 0 0 1 1 0 0 0] 2MU-MIMO 3 [0 0 0 0 1 1 0 0] 2 MU-MIMO 4 [0 0 0 0 0 1 1 0] 2 MU-MIMO 5 [00 0 0 0 0 1 1] 2 MU-MIMO 6 [1 1 1 0 0 0 0 0] 3 SU-MIMO/MU- MIMO 7 [0 0 01 1 1 0 0] 3 MU-MIMO 8 [0 0 0 0 1 1 1 0] 3 MU-MIMO 9 [0 0 0 0 0 1 1 1] 3MU-MIMO 10 [1 1 1 1 0 0 0 0] 4 SU-MIMO/MU- MIMO 11 [0 0 0 0 1 1 1 1] 4MU-MIMO 12 [1 1 1 1 1 0 0 0] 5 SU-MIMO/MU- MIMO 13 [1 1 1 1 1 1 0 0] 6SU-MIMO/MU- MIMO 14 [1 1 1 1 1 1 1 0] 7 SU-MIMO/MU- MIMO 15 [1 1 1 1 1 11 1] 8 SU-MIMO

As seen in Table 9 above, the index for rank >1 transmission layercombinations where both transport blocks are enabled requires a total of16 indices and thus can be accomplished utilizing 4 bits.

As summarized in Table 10 below, the total required is 7 bits whentransport block enabling is considered. In particular, if only onetransport block is enabled, 5 bits are required for transmission layersignaling whereas 2 bits are required for transmission rank. Conversely,if both transport blocks are enabled only 4 bits are required fortransmission of the layer information while 3 bits are required for thetotal transmission rank. In both cases, 7 total bits are required.

TABLE 10 Signaling bit when TB enabling information is considered Bitsfor Bits for Total TB enabling transmission total trans- signallinginformation layer mission rank bits One TB is enabled 5 2 7 and theother is disabled Both TB are enabled 4 3 7

5.2. Signaling with Joint Coding of Layer and Rank

An alternative to explicitly signaling total transmission rank whichcould require up to 3 bits could be to use the joint coding of both rankand layer information. For example, when considering Table 9 above, whenboth the transport blocks are enabled, 4 bits are needed to signal thetransmission layer which leads to a total of 7-bit signaling if 3-bitadditional signaling is used for total transmission rank.

Table 11 below, shows an example of a joint coding of rank and layerinformation. As will be appreciated utilizing the table, 50 combinationsare needed, requiring 6 bits for signaling. This further leads to a1-bit savings over separate coding the rank and layer information, andalso leaves 10 fields unused, which could be reserved for otherpurposes.

TABLE 11 Combined Layer and total transmission rank for 8-layertransmission Bitmap Per UE Total Indications transmis- transmis- Indexfor layers sion rank sion rank Modes 0 [1 1 0 0 0 0 0 0] 2 8 MU-MIMO 1[0 0 1 1 0 0 0 0] 2 8 MU-MIMO 2 [0 0 0 1 1 0 0 0] 2 8 MU-MIMO 3 [0 0 0 01 1 0 0] 2 8 MU-MIMO 4 [0 0 0 0 0 1 1 0] 2 8 MU-MIMO 5 [0 0 0 0 0 0 1 1]2 8 MU-MIMO 6 [1 1 1 0 0 0 0 0] 3 8 MU-MIMO 7 [0 0 0 1 1 1 0 0] 3 8MU-MIMO 8 [0 0 0 0 1 1 1 0] 3 8 MU-MIMO 9 [0 0 0 0 0 1 1 1] 3 8 MU-MIMO10 [1 1 1 1 0 0 0 0] 4 8 MU-MIMO 11 [0 0 0 0 1 1 1 1] 4 8 MU-MIMO 12 [11 1 1 1 0 0 0] 5 8 MU-MIMO 13 [1 1 1 1 1 1 0 0] 6 8 MU-MIMO 14 [1 1 1 11 1 1 0] 7 8 MU-MIMO 15 [1 1 1 1 1 1 1 1] 8 8 SU-MIMO 16 [1 1 0 0 0 0 0x] 2 7 MU-MIMO 17 [0 0 1 1 0 0 0 x] 2 7 MU-MIMO 18 [0 0 0 1 1 0 0 x] 2 7MU-MIMO 19 [0 0 0 0 1 1 0 x] 2 7 MU-MIMO 20 [0 0 0 0 0 1 1 x] 2 7MU-MIMO 21 [1 1 1 0 0 0 0 x] 3 7 MU-MIMO 22 [0 0 0 1 1 1 0 x] 3 7MU-MIMO 23 [0 0 0 0 1 1 1 x] 3 7 MU-MIMO 24 [1 1 1 1 0 0 0 x] 4 7MU-MIMO 25 [1 1 1 1 1 0 0 x] 5 7 MU-MIMO 26 [1 1 1 1 1 1 0 x] 6 7MU-MIMO 27 [1 1 1 1 1 1 1 x] 7 7 SU-MIMO 28 [1 1 0 0 0 0 x x] 2 6MU-MIMO 29 [0 0 1 1 0 0 x x] 2 6 MU-MIMO 30 [0 0 0 1 1 0 x x] 2 6MU-MIMO 31 [0 0 0 0 1 1 x x] 2 6 MU-MIMO 32 [1 1 1 0 0 0 x x] 3 6MU-MIMO 33 [0 0 0 1 1 1 x x] 3 6 MU-MIMO 34 [1 1 1 1 0 0 x x] 4 6MU-MIMO 35 [1 1 1 1 1 0 x x] 5 6 MU-MIMO 36 [1 1 1 1 1 1 x x] 6 6SU-MIMO 37 [1 1 0 0 0 x x x] 2 5 MU-MIMO 38 [0 0 1 1 0 x x x] 2 5MU-MIMO 39 [0 0 0 1 1 x x x] 2 5 MU-MIMO 40 [1 1 1 0 0 x x x] 3 5MU-MIMO 41 [1 1 1 1 0 x x x] 4 5 MU-MIMO 42 [1 1 1 1 1 x x x] 5 5SU-MIMO 43 [1 1 0 0 x x x x] 2 4 MU-MIMO 44 [0 0 1 1 x x x x] 2 4MU-MIMO 45 [1 1 1 0 x x x x] 3 4 MU-MIMO 46 [1 1 1 1 x x x x] 4 4SU-MIMO 47 [1 1 0 x x x x x] 2 3 MU-MIMO 48 [1 1 1 x x x x x] 3 3SU-MIMO 49 [1 1 x x x x x x] 2 2 SU-MIMO 50-63 Reserved

In Table 11 above, “x” indicates layers not transmitted

Another example as shown in Table 12 below for a total of 2 layertransmission, where 2 bits could be used to signal both layers and totaltransmission rank.

TABLE 12 Combined Layer and total transmission rank for 2-layertransmission Bitmap Per UE Total indication transmis- transmis- Index oflayers sion rank sion rank Mode 0 [1 x] 1 1 SU-MIMO 1 [1 0] 1 2 MU-MIMO2 [0 1] 1 2 MU-MIMO 3 [1 1] 2 2 SU-MIMO

Again, “x” in the table indicates layers not transmitted

If TB information in Rel-8 DCI format 2/2A is considered, then rank-2SU-MIMO with bitmap of layers of [1 1] in Table 12 does not need to besignaled and this index could be reserved for other purpose. To be morespecific, the following steps could be used to determine the signaling:

-   -   If both TB are enabled, no explicit signal is needed as this        implies that rank-2 SU-MIMO will be transmitted    -   Else if only one TB is enabled, using signaling in Table 13

As there exists a one-to-one mapping between layer and DRS ports, suchsignaling could also be used to signal the DRS ports, and in Table 13,port⁰ and port¹ are DRS ports corresponding to layer 0 and 1,respectively.

TABLE 13 Combined Layer and total transmission rank for 2-layertransmission Bitmap Total indication transmis- Index of layers sion rankMode DRS port 0 [1 x] 1 SU-MIMO port⁰ 1 [1 0] 2 MU-MIMO port⁰ 2 [0 1] 2MU-MIMO port¹ 3 Reserved

Again, the “x” in the table indicates layers not transmitted

Based on the above, by applying joint coding as shown in the examples,both transmit layers and total transmission rank could be signaledtogether. It should also be noted that in addition to transmit layer andtotal transmission rank, the SU-MIMO or MU-MIMO mode information is alsosignaled.

6. Signaling of DRS Ports

The signaling disclosed above could be viewed as a part of signaling ofDRS patterns/codes or DRS ports which are just divided into someintermediate steps of signaling for layers first, being followed by alayer to DRS port mapping as shown below with regard to FIG. 10.Alternatively, such signaling for DRS ports could be worked out directlyin a way that signaling could be directly mapped to a DRS port.

Reference is now made to FIG. 10. In FIG. 10, a base station 1010communicates with a UE 1020.

The signaling between base station 1010 and UE 1020 provides layer andother information to UE 1020.

As seen with reference numeral 1030, the signaling between the basestation 1010 and the UE 1020 is the equivalent to signaling the DRSports where the UE can derive the DRS ports based on a layer to DRSmapping.

However, if DRS ports are independent of the total transmission rank butonly depend on the transmission layer, this may be denoted as DRSport^(n), where n is the layer index. In this case, there will be totalof N DRS antenna ports, port^(n), n=0, . . . , N−1, where N is themaximum possible transmission layer rank. For such a case, thetransmission layer has a one-to-one mapping to the DRS port, andtherefore, all layer indices could be viewed as the DRS port indices,and the signaling of the layer index in the above embodiments may beviewed as the signaling of a DRS port index.

If the DRS ports are dependent on both the transmission layer and totaltransmission rank, then this may be denoted as port_(m) ^(n), where n isthe layer index and m is the total transmission rank. For example, port₅³, refers to a DRS port for transmission layer 3 where the totaltransmission rank is 5.

Reference is now made to Tables 14 and 15 below. These tables aremodified from Tables 6 and 11 above which include DRS ports in thesignaling table.

TABLE 14 Signaling table with DRS ports (rank information is separatelyencoded) Bitmap Per UE Indications transmis- Index for layers sion rankModes DRS port 0 [1 0 0 0 0 0 0 0] 1 SU-MIMO/MU- port_(m) ⁰ MIMO 1 [0 10 0 0 0 0 0] 1 MU-MIMO port_(m) ¹ 2 [0 0 1 0 0 0 0 0] 1 MU-MIMO port_(m)³ 3 [0 0 0 1 0 0 0 0] 1 MU-MIMO . 4 [0 0 0 0 1 0 0 0] 1 MU-MIMO . 5 [0 00 0 0 1 0 0] 1 MU-MIMO . 6 [0 0 0 0 0 0 1 0] 1 MU-MIMO 7 [0 0 0 0 0 0 01] 1 MU-MIMO 8 [1 1 0 0 0 0 0 0] 2 SU-MIMO/MU- port_(m) ⁰, MIMO port_(m)¹ 9 [0 0 1 1 0 0 0 0] 2 MU-MIMO port_(m) ², port_(m) ³ . . .

TABLE 15 Signaling table with DRS ports (rank information is jointlyencoded) Per UE Total Bitmap trans- trans- Indications mission missionInd. for layers rank rank Modes DRS port 0 [1 1 0 0 0 0 0 0] 2 8 MU-MIMOport₈ ⁰, port₈ ¹ 1 [0 0 1 1 0 0 0 0] 2 8 MU-MIMO port₈ ², port₈ ³ 2 [0 00 1 1 0 0 0] 2 8 MU-MIMO . 3 [0 0 0 0 1 1 0 0] 2 8 MU-MIMO . 4 [0 0 0 00 1 1 0] 2 8 MU-MIMO . 5 [0 0 0 0 0 0 1 1] 2 8 MU-MIMO 6 [1 1 1 0 0 0 00] 3 8 MU-MIMO port₈ ⁰, port₈ ¹, port₈ ² 7 [0 0 0 1 1 1 0 0] 3 8 MU-MIMO. 8 [0 0 0 0 1 1 1 0] 3 8 MU-MIMO . 9 [0 0 0 0 0 1 1 1] 3 8 MU-MIMO . 10[1 1 1 1 0 0 0 0] 4 8 MU-MIMO 11 [0 0 0 0 1 1 1 1] 4 8 MU-MIMO 12 [1 1 11 1 0 0 0] 5 8 MU-MIMO 13 [1 1 1 1 1 1 0 0] 6 8 MU-MIMO 14 [1 1 1 1 1 11 0] 7 8 MU-MIMO 15 [1 1 1 1 1 1 1 1] 8 8 SU-MIMO 16 [1 1 0 0 0 0 0] 2 7MU-MIMO port₇ ⁰, port₇ ¹ . . .

In Table 14, the rightmost column shows the DRS antenna ports whichcould be used by the UE for demodulation. As the total rank informationis separately encoded, the UE needs to decode the rank information m anduse that in conjunction with the DRS ports indication in the table tofind the proper DRS port for demodulation.

In Table 15, ranks are jointly encoded with the transmission layer, therightmost column shows the explicit DRS antenna ports which could beused by the UE for demodulation. In either case, the signaling describedabove could be viewed as signaling for DRS ports index.

In another example when TB enabling is considered and selected layercombinations are supported for MU-MIMO, the layers and DRS ports couldbe signaled to the UE as shown in Table 16. In the example of Table 16the total maximum layers supported in MU-MIMO is 4 and the maximumlayers per UE is 2. In this case, 3-bits are needed.

In the example of Table 16, the illustrated DRS ports for MU-MIMO onlytransmission are meant only as an example, and other DRS portscombination could be used. As for SU-MIMO, up to 8 layers may need to besupported, so 3-bits are needed to indicate the rank.

The signaling design in Table 16 is able to support both MU-MIMO andSU-MIMO transmission without explicitly indicating whether thetransmission is SU-MIMO or MU-MIMO. As 8 layers need to be supported forSU-MIMO, 3 bits are needed for signaling, as shown in Table 3 above.However, the embodiment of Table 16 adds no overhead to support bothMU-MIMO and SU-MIMO.

TABLE 16 Signaling of DRS ports (with total 4 rank in MU-MIMO) If one TBis enabled and other is disabled Both TB are enabled Bit map for DRS Bitmap for DRS Index layers ports Transmission layers ports Transmission 0[1 0 0 0 0 0 0 0] port₈ ⁰ SU/MU- [1 1 0 0 0 0 0 0] port₈ ⁰, port₈ ¹SU/MU- MIMO MIMO 1 [0 1 0 0 0 0 0 0] port₈ ¹ MU-MIMO [0 0 1 1 0 0 0 0]port₈ ², port₈ ³ MU-MIMO 2 [0 0 1 0 0 0 0 0] port₈ ² MU-MIMO [1 1 1 0 00 0 0] port₈ ⁰, port₈ ¹, port₈ ² SU-MIMO 3 [0 0 0 1 0 0 0 0] port₈ ³MU-MIMO [1 1 1 1 0 0 0 0] port₈ ⁰, . . . , port₈ ³ SU-MIMO 4 Reserved [11 1 1 1 0 0 0] port₈ ⁰, . . . , port₈ ⁴ SU-MIMO 5 Reserved [1 1 1 1 1 10 0] port₈ ⁰, . . . , port₈ ⁵ SU-MIMO 6 Reserved [1 1 1 1 1 1 1 0] port₈⁰, . . . , port₈ ⁶ SU-MIMO 7 Reserved [1 1 1 1 1 1 1 1] port₈ ⁰, . . . ,port₈ ⁷ SU-MIMO

An alternative to the solution of Table 16 is to support two types ofDRS ports for MU-MIMO simantaneously, these two types of DRS ports couldprovide different number of orthogonal DRS ports and tailor differentscenarios. As shown in Table 17, DRS ports indicated by * may not be thesame as corresponding DRS ports without *. For example, in a CDM/FDMtype of DRS design, DRS ports denoted by port₈ ⁰ . . . port; may have adifferent walsh code length as port₈ ⁰* . . . port₈ ³*, such as port₈ ⁰. . . port; having walsh code length of 2, while port₈ ⁰* . . . port₈ ³*having walsh code length of 4. The purpose of designing two types of DRSports would be to tailor different application scenarios of MU-MIMO. Forexample, when there are large number of users to be scheduled inMU-MIMO, port₈ ⁰ . . . port₈ ³* could be used, which has walsh codelength of 4, and therefore, could provide 4 orthogonal DRS ports andlead to improved performance. On the other hand, when there are lessusers to be scheduled in MU-MIMO, whose spatial separation is relativelylarge, port₈ ⁰ and port₈ ¹ could be used, whose walsh code length is 2,and therefore could provide two orthogonal DRS ports. From Table 17, itcan be seen that both types of DRS ports could be signalled withoutrequiring extra overhead and it could be up to the eNB to decide whichDRS ports are used.

TABLE 17 Signaling of two types of DRS ports (with total 4 rank inMU-MIMO) If one TB is enabled and other is disabled Both TB are enabledBit map for DRS Bit map for DRS Index layers ports Transmission layersports Transmission 0 [1 0 0 0 0 0 0 0] port₈ ⁰ SU/MU- [1 1 0 0 0 0 0 0]port₈ ⁰*, port₈ ¹* SU/MU- MIMO MIMO 1 [1 0 0 0 0 0 0 0] port₈ ⁰* SU/MU-[0 0 1 1 0 0 0 0] port₈ ²*, port₈ ³* MU-MIMO MIMO 2 [0 1 0 0 0 0 0 0]port₈ ¹ MU-MIMO [1 1 1 0 0 0 0 0] port₈ ⁰, port₈ ¹, port₈ ² SU-MIMO 3 [01 0 0 0 0 0 0] port₈ ¹* MU-MIMO [1 1 1 1 0 0 0 0] port₈ ⁰, . . . , port₈³ SU-MIMO 4 [0 0 1 0 0 0 0 0] port₈ ²* MU-MIMO [1 1 1 1 1 0 0 0] port₈⁰, . . . , port₈ ⁴ SU-MIMO 5 [0 0 0 1 0 0 0 0] port₈ ³* MU-MIMO [1 1 1 11 1 0 0] port₈ ⁰, . . . , port₈ ⁵ SU-MIMO 6 Reserved [1 1 1 1 1 1 1 0]port₈ ⁰, . . . , port₈ ⁶ SU-MIMO 7 Reserved [1 1 1 1 1 1 1 1] port₈ ⁰, .. . , port₈ ⁷ SU-MIMO

9. DCI Format to Carry Signaling

The signaling for the transmission layer could be carried on a new DCIformat designed for LTE Rel-9 or Rel-10, or could be carried in amodified Rel-8 DCI format. In the case of a modified Rel-8 DCI format,the formats for 2 or 2A in Rel-8 could be the most suitable DCI formatswhen a single DCI format covering both SU-MIMO and MU-MIMO is to bereceived by the UE.

As DRS is used for demodulation in Rel-9 and Rel-10, the transmittedprecoding matrix (TPMI) information is not needed in DCI, so the bitsthat correspond to pre-coding information in these formats could beremoved and replaced with the proposed signaling bits, which couldsignal both the transmission layers or DRS ports and, if needed, thetotal transmission rank.

For example, if the number of total transmission layers is 8, thesignaling bits for PMI could be 6 or more, and the savings on the use ofthose bits could be used for signaling layer information, which wouldalso require 5 or 6 bits. Such a modified DCI format could be used inRel-9 or Rel-10 for both SU-MIMO and MU-MIMO.

Generally, at the eNB, the same DCI formatted message may be used tocarry different information for a first and second set of UEs. Forexample a first set of UEs corresponding to Rel-8 UEs and a second setof UEs corresponding to beyond Rel-8 UEs could be used. If the targetedUE is from the first set, then the DCI formatted message will beconfigured to carry an indication of PMI. If the targeted UE is from thesecond set, the DCI formatted message will be configured to carry anindication of layers. In some embodiments, the indication of PMI and theindication of layers are represented by the same number of bits.

10. Signaling of DRS for Rank-1 MU-MIMO Transmission

The embodiments described above consider a uniform DCI format forsignaling both the SU-MIMO and MU-MIMO transmission. They are flexibleand could support all layer transmissions from 1 to 8 layers. However,in certain embodiments, it may be possible to have only rank-1transmissions that are supported for MU-MIMO. For such deployments, ifone of the proposed methods is used for signaling layers or DRS, and ifDCI formats similar to those used in 2 or 2A are used, bits such asthose corresponding to the 2nd transport block will be wasted. To avoidthe potential wastage, a more compact DCI format could be consideredwhich only contains information for one layer. In this case, the UE canbe signaled which DRS to use by an N bit long field, where 2 exp N isgreater than or equal to the total number of DRS available to the UE.

For example, if 4 DRS are used for a 4 transmit antenna rank-1 MU-MIMO,then each of the 4 UEs would be signaled 2 bits to indicate which one ofthe 4 DRSs to use. A modified version of DCI format 1D may be used forsuch rank-1 MU-MIMO transmissions where DRS assignment bits describedcould replace the TPMI information.

In a further embodiment, such a rank-1 only MU-MIMO could also be usedas a fallback mode for a more general high rank MU-MIMO. In such case,the UE could try to detect both modified DCI format 1D for rank-1MU-MIMO as well as modified DCI formats 2 or 2A for more generalhigh-rank MU-MIMO.

Based on the above, a number of configurations for MU-MIMO transmissioncould exist. In a first embodiment, a rank-1 only MU-MIMO transmissionwould be applied using a modified DCI format 1 D.

In a further configuration, it would include a high-order MIMOtransmission including both SU-MIMO and MU-MIMO, which uses a new DCIformat, or a DCI format modified from Rel-8 DCI formats 2 and 2A.

In a third configuration, the rank-1 only MU-MIMO is used as a fallbackmode for a more general high-order MIMO transmission mode. Both DCIformats from the above could be transmitted.

High-level signaling could be used to inform the UE of suchconfiguration so that the UE would know what kind of DCI formats itneeds to decode.

11. Summary of Embodiments

The signaling bits for each approach are summarized with regard to Table18 and Table 19 below. Table 18 summarizes the signaling required for 2and 4 layers. As shown, the methods require more or less the samesignaling overhead.

Table 19 summarizes the signaling overhead for 8 layers, where the mostsignaling overhead is incurred. From Table 19, it can be observed thatalthough the bitmap approach provides the most flexibility, it requiresthe most signaling bits as well. Alternatives provide group assignedapproaches and select layer approaches to reduce the overhead ofsignaling without losing flexibility. Furthermore, with the help of thetransport block enabling information and joint coding of both rank andlayer, overall signaling could be reduced even further. Comparing thejoint coding method with the bitmap method, the overall signaling bitsare almost cut in half.

TABLE 18 Summary of signaling bits for total of 2 and 4 layers TotalBits for number total of trans- Bits for trans- Total mission transmis-mission bits for Methods layers sion layer rank signaling Bitmaps 2 2 13 Approach 4 4 2 6 Group 2 2 1 3 Assignment Approach 4 4 2 6 Selected 22 1 3 Layer Approach 4 3 2 5

TABLE 19 Summary of signaling bits for total of 8 layers Total Bits fornumber total of trans- Bits for trans- Total mission transmis- missionbits for Methods layers sion layer rank signaling Bitmaps Approach 8 8 311 Group Assignment 8 6 3 9 Approach Selected Layer 8 5 3 8 ApproachSelected One TB 8 5 2 7 Layer enabled with TB Two TB 8 4 3 7 Enablingenabled Approach with separate coding Two TB 8 6 enabled with jointcoding

Furthermore, subset selections can be applied to limit the transmissionto use only selected layer combinations from the tables. For example, asubset of layer assignments for SU-MIMO can be used when the eNB wouldlike to force the transmission in SU-MIMO mode. In other scenarios,certain layers may be reserved for SPS (Semi-Persistent Scheduling)transmission and therefore, subset selections could avoid the assignmentof such layers to the UE. Such subsets could be predefined in signalsthrough broadcast channels or higher layer signals.

In some scenarios, it may beneficial to use the proposed approaches tosignal the layer assignment to a UE in a unified MIMO transmission mode,which could include MU-MIMO and SU-MIMO transmissions and allow dynamicswitching between them without awareness by the UE.

Furthermore, in some embodiments, the signaling approaches proposedabove could also be used for separate SU-MIMO and MU-MIMO transmissionmodes, that are explicitly specified semi-statically by higher-layersignaling such as RRC.

The above can be implemented on any user equipment on the receiving sideand any network element such as an evolved Node B on the sending side.On the sending side, the network element will generally include aprocessor, memory and communications subsystem to send the informationconcerning transport layers utilized.

For the UE side, FIG. 11 is a block diagram illustrating a UE capable ofbeing used with embodiments of the apparatus and method of the presentapplication. Mobile device 1100 is typically a two-way wirelesscommunication device having at least voice communication capabilities.Depending on the exact functionality provided, the wireless device maybe referred to as a data messaging device, a two-way pager, a wirelesse-mail device, a cellular telephone with data messaging capabilities, awireless Internet appliance, a mobile device, or a data communicationdevice, as examples.

Where UE 1100 is enabled for two-way communication, it will incorporatea communication subsystem 1111, including both a receiver 1112 and atransmitter 1114, as well as associated components such as one or more,typically embedded or internal, antenna elements 1116 and 1118, localoscillators (LOs) 1113, and a processing module such as a digital signalprocessor (DSP) 1120. As will be apparent to those skilled in the fieldof communications, the particular design of the communication subsystem1111 will be dependent upon the communication network in which thedevice is intended to operate.

Network access requirements will also vary depending upon the type ofnetwork 1119. An LTE UE may require a subscriber identity module (SIM)card in order to operate on the LTE or LTE-A network. The SIM interface1144 is normally similar to a card-slot into which a SIM card can beinserted and ejected like a diskette or PCMCIA card. The SIM card mayhold key configuration 1151, and other information 1153 such asidentification, and subscriber related information.

When network registration or activation procedures have been completed,UE 1100 may send and receive communication signals over the network1119. As illustrated in FIG. 11, network 1119 can consist of multipleantennas communicating with the UE. These antennas are in turn connectedto an eNB 1170.

Signals received by antenna 1116 through communication network 1119 areinput to receiver 1112, which may perform such common receiver functionsas signal amplification, frequency down conversion, filtering, channelselection and the like, and in the example system shown in FIG. 11,analog to digital (A/D) conversion. A/D conversion of a received signalallows more complex communication functions such as demodulation anddecoding to be performed in the DSP 1120. In a similar manner, signalsto be transmitted are processed, including modulation and encoding forexample, by DSP 1120 and input to transmitter 1114 for digital to analogconversion, frequency up conversion, filtering, amplification andtransmission over the communication network 1119 via antenna 1118. DSP1120 not only processes communication signals, but also provides forreceiver and transmitter control. For example, the gains applied tocommunication signals in receiver 1112 and transmitter 1114 may beadaptively controlled through automatic gain control algorithmsimplemented in DSP 1120.

UE 1100 may include a microprocessor 1138 which controls the overalloperation of the device. Communication functions, including data andvoice communications, are performed through communication subsystem1111. Microprocessor 1138 also interacts with further device subsystemssuch as the display 1122, flash memory 1124, random access memory (RAM)1126, auxiliary input/output (I/O) subsystems 1128, serial port 1130,one or more keyboards or keypads 1132, speaker 1134, microphone 1136,other communication subsystem 1140 such as a short-range communicationssubsystem and any other device subsystems generally designated as 1142.Serial port 1130 could include a USB port or other port known to thosein the art.

Some of the subsystems shown in FIG. 11 perform communication-relatedfunctions, whereas other subsystems may provide “resident” or on-devicefunctions. Notably, some subsystems, such as keyboard 1132 and display1122, for example, may be used for both communication-related functions,such as entering a text message for transmission over a communicationnetwork, and device-resident functions such as a calculator or tasklist.

Operating system software used by the microprocessor 1138 is generallystored in a persistent store such as flash memory 1124, which mayinstead be a read-only memory (ROM) or similar storage element (notshown). Those skilled in the art will appreciate that the operatingsystem, specific device applications, or parts thereof, may betemporarily loaded into a volatile memory such as RAM 1126. Receivedcommunication signals may also be stored in RAM 1126.

As shown, flash memory 1124 can be segregated into different areas forboth computer programs 1158 and program data storage 1150, 1152, 1154and 1156. These different storage types indicate that each program canallocate a portion of flash memory 1124 for their own data storagerequirements. Microprocessor 1138, in addition to its operating systemfunctions, preferably enables execution of software applications on theUE. A predetermined set of applications that control basic operations,including at least data and voice communication applications forexample, will normally be installed on UE 1100 during manufacturing.Other applications could be installed subsequently or dynamically.

One software application may be a personal information manager (PIM)application having the ability to organize and manage data itemsrelating to the user of the UE such as, but not limited to, e-mail,calendar events, voice mails, appointments, and task items. Naturally,one or more memory stores would be available on the UE to facilitatestorage of PIM data items. Such PIM application would generally have theability to send and receive data items, via the wireless network 1119.In one embodiment, the PIM data items are seamlessly integrated,synchronized and updated, via the wireless network 1119, with the UEuser's corresponding data items stored or associated with a hostcomputer system. Further applications may also be loaded onto the UE1100 through the network 1119, an auxiliary I/O subsystem 1128, serialport 1130, short-range communications subsystem 1140 or any othersuitable subsystem 1142, and installed by a user in the RAM 1126 or anon-volatile store (not shown) for execution by the microprocessor 1138.Such flexibility in application installation increases the functionalityof the device and may provide enhanced on-device functions,communication-related functions, or both. For example, securecommunication applications may enable electronic commerce functions andother such financial transactions to be performed using the UE 1100.

In a data communication mode, a received signal such as a text messageor web page download will be processed by the communication subsystem1111 and input to the microprocessor 1138, which may further process thereceived signal for element attributes for output to the display 1122,or alternatively to an auxiliary I/O device 1128.

A user of UE 1100 may also compose data items such as email messages forexample, using the keyboard 1132, which may be a complete alphanumerickeyboard or telephone-type keypad in some embodiments, in conjunctionwith the display 1122 and possibly an auxiliary I/O device 1128. Suchcomposed items may then be transmitted over a communication networkthrough the communication subsystem 1111.

For voice communications, overall operation of UE 1100 is similar,except that received signals would typically be output to a speaker 1134and signals for transmission would be generated by a microphone 1136.Alternative voice or audio I/O subsystems, such as a voice messagerecording subsystem, may also be implemented on UE 1100. Although voiceor audio signal output is generally accomplished primarily through thespeaker 1134, display 1122 may also be used to provide an indication ofthe identity of a calling party, the duration of a voice call, or othervoice call related information for example.

Serial port 1130 in FIG. 11 would normally be implemented in a personaldigital assistant (PDA)-type UE for which synchronization with a user'sdesktop computer (not shown) may be desirable, but is an optional devicecomponent. Such a port 1130 would enable a user to set preferencesthrough an external device or software application and would extend thecapabilities of UE 1100 by providing for information or softwaredownloads to UE 1100 other than through a wireless communicationnetwork. The alternate download path may for example be used to load anencryption key onto the device through a direct and thus reliable andtrusted connection to thereby enable secure device communication. Aswill be appreciated by those skilled in the art, serial port 1130 canfurther be used to connect the UE to a computer to act as a modem.

Other communications subsystems 1140, such as a short-rangecommunications subsystem, is a further component which may provide forcommunication between UE 1100 and different systems or devices, whichneed not necessarily be similar devices. For example, the subsystem 1140may include an infrared device and associated circuits and components ora Bluetooth™ communication module to provide for communication withsimilarly enabled systems and devices. Subsystem 1140 may also be usedfor WiFi or WiMAX communications.

The embodiments described herein are examples of structures, systems ormethods having elements corresponding to elements of the techniques ofthis application. This written description may enable those skilled inthe art to make and use embodiments having alternative elements thatlikewise correspond to the elements of the techniques of thisapplication. The intended scope of the techniques of this applicationthus includes other structures, systems or methods that do not differfrom the techniques of this application as described herein, and furtherincludes other structures, systems or methods with insubstantialdifferences from the techniques of this application as described herein.

The invention claimed is:
 1. A method performed by a network element ofa multiple input multiple output ‘MIMO’ system, the method comprising:transmitting downlink control information ‘DCI’ that containsinformation regarding transport blocks to be utilized by a userequipment ‘UE’ and regarding dedicated reference signal ports to beutilized by the UE, the DCI further comprising an index value; whereinif the information signifies that one transport block is used, a firstset of layer combinations or associated combinations of dedicatedreference signal ports is selected, wherein if the information signifiesthat two transport blocks are used, a second set of layer combinationsor associated combinations of dedicated reference signal ports isselected; and determining a layer combination or associated combinationof dedicated reference signal ports to be utilized by the UE from theselected set of layer combinations or associated combinations ofdedicated reference signal ports and the index value; wherein the layercombination or associated combination of dedicated reference signalports is uniquely determined by the selected set of layer combinationsor associated combinations of dedicated reference signal ports and theindex value.
 2. The method of claim 1 wherein the information, which iscontained in the DCI, supports multiple-user MIMO transmissions.
 3. Themethod of claim 1 wherein a scrambling code is associated with the indexvalue.
 4. The method of claim 1 wherein the network element is an eNodeBcapable of at least one of long term evolution ‘LTE’ operations andLTE-advanced operations.
 5. A network element of a multiple inputmultiple output ‘MIMO’ system, comprising: a processor configured toexecute instructions that cause transmission of downlink controlinformation ‘DCI’ that contains information regarding transport blocksto be utilized by a user equipment ‘UE’ and regarding dedicatedreference signal ports to be utilized by the UE, the information furthercomprising an index value; wherein if the information signifies that onetransport block is used, a first set of layer combinations or associatedcombinations of dedicated reference signal ports is selected, wherein ifthe information signifies that two transport blocks are used, a secondset of layer combinations or associated combinations of dedicatedreference signal ports is selected; and wherein the processor is furtherconfigured to determine a layer combination or associated combination ofdedicated reference signal ports to be utilized by the UE from theselected set of layer combinations or associated combinations ofdedicated reference signal ports and the index value; wherein the layercombination or associated combination of dedicated reference signalports is uniquely determined by the selected set of layer combinationsor associated combinations of dedicated reference signal ports and theindex value.
 6. The network element of claim 5 wherein the information,which is contained in the DCI, supports multiple-user MIMOtransmissions.
 7. The network element of claim 5 wherein a scramblingcode is associated with the index value.
 8. The network element of claim5 wherein the network element is an eNodeB capable of at least one oflong term evolution ‘LTE’ operations and LTE-advanced operations.
 9. Anon-transitory computer-readable medium storing instructions which, whenexecuted by a processor of a network element, cause the processor to:transmit downlink control information ‘DCI’ that contains informationregarding transport blocks to be utilized by a user equipment ‘UE’ andregarding dedicated reference signal ports to be utilized by the UE, theinformation further comprising an index value; wherein if theinformation signifies that one transport block is used, a first set oflayer combinations or associated combinations of dedicated referencesignal ports is selected, wherein if the information signifies that twotransport blocks are used, a second set of layer combinations orassociated combinations of dedicated reference signal ports is selected;and determine a layer combination or associated combination of dedicatedreference signal ports to be utilized by the UE from the selected set oflayer combinations or associated combinations of dedicated referencesignal ports and the index value; wherein the layer combination orassociated combination of dedicated reference signal ports is uniquelydetermined by the selected set of layer combinations or associatedcombinations of dedicated reference signal ports and the index value.10. The non-transitory computer-readable medium of claim 9 wherein theinformation, which is contained in the DCI, supports multiple-user MIMOtransmissions.
 11. The non-transitory computer-readable medium of claim9 wherein a scrambling code is associated with the index value.
 12. Thenon-transitory computer-readable medium of claim 9 wherein the networkelement is an eNodeB, and wherein the instructions cause the networkelement to perform the transmission of DCI at least one of long termevolution ‘LTE’ operations and LTE-advanced operations.
 13. A userequipment ‘UE’ comprising: a processor configured to executeinstructions that cause the UE to: receive downlink control information‘DCI’ that contains information regarding transport blocks to beutilized and regarding dedicated reference signal ports to be utilized,the information further comprising an index value; wherein if theinformation signifies that one transport block is used, a first set oflayer combinations or associated combinations of dedicated referencesignal ports is selected, wherein if the information signifies that twotransport blocks are used, a second set of layer combinations orassociated combinations of dedicated reference signal ports is selected;and determine a layer combination or associated combination of dedicatedreference signal ports to be utilized by the UE from the selected set oflayer combinations or associated combinations of dedicated referencesignal ports and the index value; wherein the layer combination orassociated combination of dedicated reference signal ports is uniquelydetermined by the selected set of layer combinations or associatedcombinations of dedicated reference signal ports and the index value.14. The UE of claim 13 wherein the information, which is contained inthe DCI, supports multiple-user MIMO transmissions.
 15. The UE of claim13 wherein a scrambling code is associated with the index value.
 16. TheUE of claim 13 wherein the instructions cause the UE to perform thereceipt of DCI during at least one of long term evolution ‘LTE’operations and LTE-advanced operations.
 17. The UE of claim 13 whereinthe instructions further cause the UE to utilize at least one of saidtransport blocks and said dedicated reference signal ports based on theinformation contained in the DCI.